446 E.. B. Wilson—The early stages of Renilla. 
ArT. XLVIII.—The early stages of Renilla; by Epmunp B. 
ILSON. With Plate VIIl.—Note from the Chesapeake Zo- 
it 
ologicai Laboratory of the Johns Hopkins University. 
DuRING the past summer, while at Beaufort, N. C., I had an 
opportunity to study the development of the colony of Renilla 
reniformis Cuv., from the simple free-swimming young to the 
adult stage. Since very little is known concerning the growth 
of the colony in the Pennatulacea and the mode of budding in 
Renilla is somewhat remarkable, a brief abstract of the observa- 
tions may be worth recording. In a fuller paper, to be else- 
where published, the intermediate stages will be figured and 
the anatomical details fully described. 
The young polyp (fig. 1) is ciliated, and at first swims actively 
at the surface. ‘T'wo slight elevations, a, a, indicate the rudi- 
ments of the first pair of zooids. The septa (indicated by dot- 
ted lines) are of unequal lengths and are disposed in accord- 
ance with a perfect bilateral symmetry. Thus, the pair on the op- 
posite side from the zooids (which may be called the lower side) 
are the shortest, not extending as far back as the level of the 
ape of zooids; the upper pair extend to the zooids; the upper 
ateral pair are apparently continuous with the longitudinal 
septum (s) which extends to the extremity of the body; and 
the lower lateral pair extend some distance beyond the pair of 
zooids. This arrangement of the septa is very constant and 
may be traced up to a late stage. And the mesenterial fila- 
ments, which appear later, are of corresponding lengths. 
Figure 2 represents the young polyp some time (probably 
about two weeks) after the free-swimming life has been aban- 
doned. Hight pinnate tentacles have appeared, the lateral 
zooids have become divided into chambers by the development 
of rudimentary septa, and a median zooid (A) has appeared on 
the upper side in front of the lateral zooids, The small or 
“ventral” compartment of each Jateral zooid is on its outer 
side, that is, the lower side when the zooid is horizontally ex- 
ten The corresponding chamber of the median zooid is on 
its posterior side, that is, the side opposite to the oral end of the 
primitive polyp. e median zooid ultimately becomes the 
peculiar central zooid through which the contained water of 
the colony is mainly discharged ; and hence the term “ Haupt- 
zooid,” which has been applied to it by German writers, is in- 
appropriate. The characteristic spicules make their appearance 
about a week after the free-swimming life is abandoned ata 
considerably earlier stage than fig. 2. 
Figure 3 represents a much later stage. The lateral zooids, 
